Nanogenerators (NGs) are nanometer-scale devices that use piezoelectric materials to harvest mechanical energy from ambient sources. Owing to the superior mechanical and electromechanical properties of nanoscale structures, NGs have demonstrated promising capability in scavenging energy from mechanical deflections, acoustic waves, fluid or air flows, and even human activities. The output of NGs has reached the sub-milliwatt level, which is sufficient to power many small electronic devices, such as light-emitting diodes (LEDs), laser diodes, pH sensors, UV sensors, speed/weight sensors, and toxic pollutant sensors. The piezoelectric output of NGs has also been used to directly drive electrochemical reactions including lithium ion intercalation, electrodegradation of dyes, and electrochemical water splitting. However, although promising, current designs for NGs still require bendable or deflecting components for mechanical energy conversion, making them difficult to integrate with regular electronic devices. Furthermore, fabrication of NGs typically relies on the large-scale integration of nanostructures, which has proven to be a critical obstacle for scaling up the manufacturing of NGs.